The present invention relates to a semiconductor and a method for driving the same, and more particularly, to a bit line equalizer for a semiconductor device.
Semiconductor memory devices define a precharge time (TRP). The precharge time (TRP) is used as one of criteria for estimating operating speed of semiconductor devices and semiconductor memory devices. As semiconductor devices and semiconductor memory devices are more highly integrated and operate at a higher speed, a voltage level of an externally applied power supply voltage is lowered. As a result, as internal circuits of the semiconductor devices operate at the lowered power supply voltage, the specification of the precharge time (TRP) becomes difficult to satisfy.
FIG. 1 is a circuit diagram of a core region of a conventional semiconductor memory device. As shown, bit lines BL and BLB and a pull-up power line RTO and a pull-down power line SB of a bit line sense amplification unit BLSA are equalized with a precharge voltage VBLP in response to a bit line equalization drive signal BLEQ.
BISH, YS, SIO and SIOB in FIG. 1 are a bit line separation high signal, a column selection signal and a segment data bus pair, respectively.
FIG. 2 is a circuit diagram of a conventional equalizing signal generating unit. As shown, the conventional equalizing signal generating unit includes a first PMOS transistor MP1 and a first NMOS transistor MN1. The first PMOS transistor MP1 forms a current path between a power supply voltage terminal POWER and a node N1 in response to a drive signal BLEQB. The first NMOS transistor MN1 forms a current path between a ground voltage terminal VSS and the node N1 in response to the drive signal BLEQB.
The conventional equalizing signal generating unit outputs a bit line equalization drive signal BLEQ through the node N1 in response to the drive signal BLEQB. A boosted voltage VPP or a power supply voltage VDD is generally used as the voltage at the power supply voltage terminal POWER. The boosted voltage VPP has low efficiency because it is generated by boosting the power supply voltage VDD in the semiconductor device. Nevertheless, in a case where the precharge time (TRP) is important, the conventional equalizing signal generating unit needs to use the boosted voltage VPP.
When the boosted voltage VPP is used as an operation power source of the bit line equalization drive circuit, the precharge time (TRP) easily can be satisfied, although current consumption may be increased. On the contrary, when the power supply voltage VDD is used as an operation power source of the bit line equalization drive circuit, because the voltage level of the supply voltage VDD is low, the precharge time (TRP) may become difficult to satisfy although the current consumption may be reduced.
FIG. 3 is a timing diagram illustrating internal operations of a conventional semiconductor memory device. Referring to FIG. 3, a precharge command PCG is applied, for example, after a precharge time (TRP) from the application of an active command ACT. If the precharge operation is performed late, the next active command is applied late, which results in deterioration of the operation characteristics.